Hi Shravan, That is really cool. Can you share with us your modifications to the script and the command line you used? I would like to try this at my home where I see like 20 APs from my neighbors and compare it to the plot of the wi-spy.
Thomas On 12/5/06, Shravan Rayanchu <[EMAIL PROTECTED]> wrote:
> Nevertheless, there is a spectrum sweep example > (gnuradio-example/usrp/usrp_spectrum_sense.py). This application can > sense a large bandwidth, but not in real time! It can do a sweep over > a very large frequency range, but it will very likely not be able to > detect bluetooth (since it is frequency hopping) nor 802.11b/g since > this will most likely just look like noise. Anyway, it is difficult to > just detect wi-fi without trying to decode it, since it is not a > continuous signal, i.e., packet oriented. Therefore, you won't have a > nice peak in your fft, compared to a radio broadcast channel. Actually, you get a reasonable plot. Although you can only sense a maximum of ~6 Mhz at once, doing so in steps of frequency gives a fair idea. I made some changes to the spectrum_sense example, so as to a fftshift and remove outer 25% of the bins. I used a frequency step of 0.5 Mhz and also passed it through the log10 block. Attached are the plots for entire spectrum (spec.pdf) and channel 1 (0.5m.pdf). Although, I am not sure what the "UNITS" are, they should give a sense of the relative powers at different frequencies. (Would they end up in dB as I passed it through the log10 block? I couldnt particularly understand Eric's code i.e. what is passed to the log10 block) Thanks, Shravan
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